1. Field of the Invention
This disclosure relates to a field of semiconductor manufacturing, and in particular relates to a treating method to be used after etching by use of a metal hard mask.
2. Description of the Related Art
In the field of semiconductor manufacturing, an opening is generally formed in a stacked structure by etching. FIG. 1A schematically illustrates a stacked structure with an opening after etching. As illustrated in FIG. 1A, on a semiconductor substrate 110, an opening 150 is formed by etching in a stacked structure of a dielectric layer 120, an intermediate layer 130 and a metal hard mask layer 140 arranged in order from bottom to top. The metal hard mask layer 140 may be used for interconnection technology employing a dielectric material with a low dielectric constant (i.e., low-k), and it may, for example, be formed of titanium nitride (TiN) or the like.
Due to etching, a large amount of etching residues (not shown in FIG. 1A) exist on the sidewalls and bottom of the opening and on the stacked structure, which will deteriorate performances of the semiconductor device. Therefore, after etching a cleaning process is generally performed on the stacked structure with the opening so as to remove the etching residues.
The present inventors have conducted in-depth investigation on post-etch treating methods in the prior art, and have found that the following problems exist.
For example, the dielectric layer 120 is generally corroded by the cleaning solution used for removing the etching residues, which is particularly notable when the dielectric layer 120 is formed of a porous material. FIG. 1B schematically illustrates a sectional view of the stacked structure with the opening after the cleaning process. As illustrated in FIG. 1B, as a result of the corrosion by the cleaning solution during the cleaning process used for removing the etching residues, a gap 160 is generated at an interface between the dielectric layer 120 and the intermediate layer 130 on the sidewalls of the opening 150, i.e., a necking phenomenon occurs. Incidentally, since the materials of the intermediate layer 130 and the metal hard mask layer 140 are generally denser than that of the dielectric layer 120, a gap formed at an interface between the intermediate layer 130 and the metal hard mask layer 140 (not shown in FIG. 1B) is generally smaller than that at the interface between the dielectric layer 120 and the intermediate layer 130; moreover, as for the gap 160 at the interface between the dielectric layer 120 and the intermediate layer 130, the part of the gap on the side of the intermediate layer 130 is smaller than the part of the gap on the side of the dielectric layer 120.
In addition, the metal hard mask layer 140 formed of titanium nitride or the like generally causes a high tensile stress, which may further aggravate significantly the necking phenomenon during the cleaning process used for removing the etching residues.
The occurrence of the necking phenomenon will seriously affect the formation of layers (such as a barrier layer and a seed layer) in the opening 150, thereby the process window for subsequent deposition will become smaller, and the contact resistance (Rc) and sheet resistance (Rs) of a metal (such as copper) subsequently filling the opening 150 can not reach target values.